Heat exchangers are designed to efficiently transfer heat between a working fluid inside the heat exchanger and another fluid, such as the atmosphere, outside the heat exchanger, or between two fluids in primary and secondary circuits within the heat exchanger.
If debris or contaminants enter the working fluid, these can build up on the internal passages of the heat exchanger, reducing its efficiency. The debris may be, for example, metals or plastics that are worn off from the heat exchanger or from other portions of a fluid circuit connected to the heat exchanger. The heat exchanger may have comparatively small cross-sections for the internal tube(s) and often there are changes in direction leading to areas where flow speeds can reduce or stagnate. Consequently, contaminants may more readily get lodged in the heat exchanger than in other parts of the fluid circuit and this leads to a loss in performance. There is also a possibility of loss in heat exchanger performance arising from degradation of the walls of the heat exchanger.
Heat exchangers made using modern techniques, such as additive manufacturing can have less well-understood degradation profiles over time compared to traditionally manufactured heat exchangers. The impact of contaminants may also be less well understood. In some cases, more care may need to be taken to avoid losses in performance from degradation and/or build-up of contaminants, which can lead to increased frequency of maintenance and/or increased frequency of inspection, in some cases involving taking the heat exchanger out of service. This then means that there can be losses in performance for the heat exchanger due to unnecessary maintenance even when there has been no loss in performance due to build-up of contaminants or degradation of the heat exchanger. There is a need to be able to effectively operate heat exchangers including additive manufactured heat exchangers without such unnecessary inspection and maintenance, and without the risk of excessive reductions in heat exchanger performance. In the past, the performance of heat exchangers has been monitored using temperature sensors in order to identify when performance is reducing and thereby predict when maintenance may be required. However, there is still a need for improved monitoring of heat exchangers.